//通过class获取元素，返回的是数组。
function getElementsByClass(name,type){
	var r=[];
	var re=new RegExp("(^|\\s)"+name+"(\\s|$)");
	var elem=document.getElementsByTagName(type||"*");
	for(var i=0;i<elem.length;i++){
		if(re.test(elem[i].className)) r.push(elem[i]);
		}
		return r;
	}
function nav(lis,cons){
    var timer = null;
	for(var i=0;i<lis.length;i++){
	  lis[i].index = i;
	  lis[i].onmouseover = function(){change(this.index)}
	  lis[i].onmouseout = function(){conHidden(this.index)}
	  
	}
	
	function change(v){
		for(var i=0;i<lis.length;i++){
		cons[i].style.display = v == i ? "block" :"none";
		}
	}
	
	function conHidden(v){
		cons[v].style.display = "none";
	}
}


var lis = document.getElementById("nav").getElementsByTagName("li");
var cons = getElementsByClass("con","div");
nav(lis,cons);